Blues head coach Antonio Conte has informed the Spain striker he is surplus to requirements at Stamford Bridge, with the pair having fallen out in January over Chelsea's reported refusal to allow Costa to move to the Chinese Super League.

Costa has been Chelsea's top scorer in each of his three seasons with the Blues, including two title wins, and remains at the club, with Atletico Madrid's interest in re-signing the striker complicated by their transfer ban.

Alvaro Morata has arrived from Real Madrid to plug the gap left by Costa, but Cahill says he will prove difficult to replace.

"As a player, he will be missed," Cahill told talkSPORT.

"Diego Costa is Diego Costa. He scores goals. He is an animated character and he is a big personality.

"He will be a big miss. We have obviously added to the squad with Alvaro and that is a great addition to the squad, but you are always to going miss big players."

Conte reaffirmed to Sky Sports on Wednesday that Costa's situation at the club remained unchanged, and confirmed the Blues' transfer business is yet to be completed.

Tiemoue Bakayoko, Antonio Rudiger and Willy Caballero have arrived alongside Morata, but Conte says the signings made by Chelsea's Premier League rivals mean defending their title is a tough prospect.

He said: "Every season I think it's right every great team tries to improve the quality of the team.

"For sure, these teams [Chelsea's title rivals] are very strong, they improved a lot. For this reason, this challenge will be very tough.

"I hope to improve our squad, our team. The transfer market is not finished. We want to be competitive and we want to try to fight this season for the title. My club knows very well what are my priorities."